Field
Embodiments of the present disclosure generally relate to apparatus for thermally processing a substrate. More specifically, embodiments described herein relate to apparatus for a rotating substrate laser anneal.
Description of the Related Art
Integrated circuits have evolved into complex devices that can include millions of transistors, capacitors, and resistors on a single chip. The evolution of chip design continually requires faster circuitry and greater circuit density that demand increasingly precise fabrication processes. One such fabrication process frequently utilized is ion implantation processes.
While various other integrated circuit fabrication processes are frequently utilized, ion implantation is particularly important in forming transistor structures on semiconductor substrate and may be repeated many times during chip fabrication. During ion implantation, a semiconductor substrate is bombarded by a beam of electrically charged ions, commonly referred to as dopants. Ion implantation changes the properties of the materials in which the dopants are implanted in order to achieve a particular level of device performance.
During ion implantation, implanted films may develop a high level of internal stress. In order to relieve the stress by repairing the crystal matrix of an implanted film and to further control the resulting properties of the implanted film, the film is typically subjected to a thermal process, such as annealing. Annealing is typically performed in a rapid thermal processing (RTP) chamber that subjects the substrate to a very brief, yet highly controlled thermal cycle to align dopants within the crystal matrix of the implanted film. However, the movement of dopant atoms within the implanted film may exceed a desired zone of occupation for the dopants if too much heat is applied, or if heat is applied for too long a time.
As devices become smaller, the target dopant zone also becomes smaller, making the task of aligning dopants in the crystal matrix while preventing undesirable diffusion beyond the target zone increasingly difficult. Nanosecond anneals utilizing megawatt lasers may be suitable in certain instances, but such tools are often very large and too expensive to implement cost-effectively.
FIG. 1 illustrates a simplified isometric view of a prior art RTP chamber. A processing chamber 100 includes a contactless or magnetically levitated substrate support 104, a chamber body 102, having walls 108, a bottom 110, and a top 112 defining an interior volume 120. The walls 108 typically include at least one substrate access port 148 to facilitate entry and egress of a substrate 140 (a portion of which is shown in FIG. 1). The access port may be coupled to a transfer chamber (not shown) or a load lock chamber (not shown) and may be selectively sealed with a valve, such as a slit valve (not shown). The substrate support 104 may be annular. The chamber 100 includes a radiant heat source 106 disposed in an inside diameter of the substrate support 104.
The substrate support 104 is adapted to magnetically levitate and rotate within the interior volume 120, so that the substrate support 104 is capable of rotating while raising and lowering vertically during processing. A window 114 made from a material transparent to heat and light of various wavelengths may be used to shield the radiant heat source 106 from the processing environment while allowing the radiant heat source 106 to heat the substrate 140. The window 114 may include a plurality of lift pins 144 coupled through an upper surface of the window 114.
The radiant heat source 106 may be a lamp assembly formed from a housing which includes a plurality of honeycomb tubes 160 coupled to a coolant source 183. The housing may be made of a copper material or other suitable material having suitable coolant channels formed therein for flow of the coolant from the coolant source 183.
The chamber 100 may also include one or more sensors 116, which are generally adapted to detect the elevation of the substrate support 104 (or substrate 140) within the interior volume 120 of the chamber body 102. The sensors 116 may be coupled to the chamber body 102 and/or other portions of the processing chamber 100 and are adapted to provide an output indicative of the distance between the substrate support 104 and the top 112 and/or bottom 110 of the chamber body 102, and may also detect misalignment of the substrate support 104 and/or substrate 140.
The RTP chamber 100 may also include a cooling block 180 adjacent to, coupled to, or formed in the top 112. Generally, the cooling block 180 is spaced apart and opposing the radiant heat source 106. The cooling block 180 comprises one or more coolant channels 184 coupled to an inlet 181A and an outlet 181B. The cooling block 180 may include a reflector coupled to a surface of the cooling block 180 facing the substrate support 104.
The RTP chamber 100, using lamp heat sources, may have a time constant that is too large for some applications. Lamp heat sources, and the housing surrounding them, may heat or cool too slowly to perform effective annealing without significant dopant diffusion in some cases.
Thus, what is needed in the art are improved apparatus for rapid thermal processing.